of Gasteropodous Mollusca. 409 



of digestion, and is highly complicated and of great extent, filling 

 by far the largest portion of the body. Each individual possesses 

 both male and female organs, as well as the additional apparatus 

 of a spermatheca, as observed in the Nudibranchs. The external 

 orifices are placed on the right side of the body and are three in 

 number ; two immediately below the eye, and one nearly half-way 

 along the body. Of the two anterior orifices, the one in front 

 is that of the male intromittent organ (PI. XX. fig. 4 a), and the 

 other, which is close behind it, is that for the passage of the ova 

 (/) ; the third orifice {m) is in communication with the sperma- 

 theca, and is that by which impregnation is efi'ected. Of the 

 position and nature of these orifices there can be no doubt, for 

 we have had frequent opportunities of observing the animals 

 during coitus, and have also seen them when spawning. The 

 male intromittent organ lies doubled upon itself immediately 

 within the orifice, and when partially exserted (fig. 4 a) is of a 

 subconic form, but is capable of much elongation and attenua- 

 tion. The point (figs. 4 6 & 5 A) is furnished with a minute curved 

 crystalline spur-like process, which is perforated (fig. 6 a). The 

 base of this process is united to a tube (figs. 4c & 5 c), which, pass- 

 ing through the axis of the penis, runs a short way backwards 

 and is joined by the oviduct at^', immediately after it is united to 

 the duct of the testis at ff, and then terminates in an elliptical 

 bulb {p) at the end of the copulatory passage, just where it receives 

 the duct of the spermatheca (r). Near to the point where the 

 oviduct joins this tube, it is attached to what occasionally assumes 

 the appearance, in the compressor, of two elongated glands (m) 

 with undulated walls, but which is very possibly a portion of the 

 large mucous gland belonging to the female parts, afterwards to 

 be more fully described. In tracing the male organs backwards, 

 it is seen that the duct of the testis, after its union with the 

 tube of the penis, runs for a short way parallel to the copulatory 

 channel, as will be by and by more particularly mentioned ; and 

 after communicating with it at/, soon reaches the median line of 

 the body, about midway between the head and the tail. The 

 duct of the testis then suddenly dilates, and, almost directly 

 afterwards, divides into two branches, one going to each side of 

 the body {d d) ; here these branches again divide into two nearly 

 equal portions, one of which goes towards the head, the other 

 towards the tail ; these portions divide and subdivide two or thi'ee 

 times, the extremities ending in blind sacs. This multiple organ, 

 there can be no doubt, is the testis, though we have no direct evi- 

 dence in proof of this. Its anatomical relationship, however, 

 appears sufficient to warrant this opinion. 



The ovarium (// h h), like the testis, is also divided into two 

 parts ; one, much the larger [h h), occupies the posterior portion 



